Shrinkproofing of wool with n, n&#39;-methylene bis-acrylamide polymerized in situ and the modified wool



1951 c. E. PARDO, JR. ET AL 3,005,730

SHRINKPROOFING OF WOOL WITH N,NMETHYLENE BIS-ACRYLAMIDE POLYMERIZED INSITU AND THE MODIFIED WOOL Filed 001:. 25, 1954 --Protein fiber (Wool) lImpregnate fiber with solution of reducing agent 2/ such as hydrazinesulphate,

ferrous sulphate, alkali metal bisulphite, etc.

Impregnate fiber with solution of N,N'-methylene bis-acrylamicle andoxidizing agent, e.g.,hydrogen peroxide, benzoyl peroxide, tert. butylhydroperoxide, etc.

/ Protein fiber (Wool) 5 having N,N'-methylene 4 bis-acrylamidepolymerized in situ thereon Reducing agent and oxidizing agentconstitute a redox catalyst INVENTORS system BY C.E.Pardo,Jr. and HP.Lundgren United States Patent Ofiice 3,005,730 Patented Oct. 24, 1961 Anon-exclusive, irrevocable, royalty-free license in the invention hereindescribed, for all governmental purposes, throughout the world, with thepower to grant sublicenses for such purposes, is hereby granted to theGovernment of the United States of America.

This invention related to processes for shrinkproofing and feltproofingproteinous fibers, particularly wool. A

particular aspect of the invention concerns the provision of processwhere N,N-methylene bis-acrylamide is polymerized on the fibers wherebyto produce a modified fiber which exhibitis a marked resistance toshrink-age as compared with the original fiber. Further objects andadvantages of the invention will be obvious from the description herein.

It is well known that laundering causes severe shrinkage of woolentextiles. This technical disadvantage seriously restricts theapplications of wool in the textile industry and much research has beenundertaken to modify the natural fiber to reduce its shrinkageproperties. In general treatments wherein resinous materials are coatedon or formed in the fiber have given the desired result of reducingshrinkage but in most cases so much of the resinous material must beincorporated in the wool that the modified fiber lacks the hand of thenatural fiber, tending to be somewhat harsh or even boardy.

It has now been-found that when the compound N,N'- methylenebis-acrylamide is polymerized in situ in the fibers, the resultingmodified fiber exhibits a drastically decreased shrinkage as comparedwith the original fiber. At the same time, only a small proportion ofthe amide need be incorporated in the fiber to obtain this efiect sothat the modified fiber has virtually the same hand as the untreatedfiber. In addition, it has been observed that this treatment does notcause any discoloration of the fiber nor does it impair tensilestrength.

The shrinkproofing treatment in accordance with this invention involvesessentially applying N,N'-methylene bis-acrylamide to the wool in thepresence of a redox catalyst system. Such a system includes a reducingagent and an oxidizing agent, the interaction of these agents providingfree radicals which cause polymerization of the amide on the wool. Anyof the redox catalyst systems suitable for the polymerization of vinylcompounds can be used. Thus for example the reducing agent may be aferrous salt such as ferrous sulphate, acetate, phosphate,ethylenediaminetetraacetate, etc.; an alkali metal bisulphite orsulphite; sulphur dioxide; sulphurous acid and so forth. It is preferredto use a salt of hydrazine as the reducing agent because when suchreagent is used the treated wool is whiter than the original wool. Thisis in contrast to the use of ferrous salts in which case the treatedwool is often stained or discolored. The important aspect of thepreferred reducing agent is the presence of the hydrazine radical; theacid moiety of the salt may be derived from any acid, as for example,bydrochloric, hydrobromic, sulphuric, sulphurous, phosphoric, benzoic,acetic, etc. The hydrazine may be completely or only partly salified bythe acid.

As the oxidizing agent in the redox system one may use such agents ashydrogen peroxide, benzoyl peroxide, acetyl peroxide, tertiary butylhydroperoxide, alkali metal involves first impregnating the fiber with asolution of a reducing agent. The fiber containing the reducing agent isthen put into a bath containing the amide and the oxidizing agentwhereby the amide will be polymerized on the fiber. If desired thesequence may be altered so that the fiber is first impregnated with theamide and one of the redox pair, for instance the reducing agent. Theimpregnated fiber is then placed in a bath containing the other redoxcatalyst (the oxidizing agent in this case) whereby the amide will bepolymerized on the fiber. Other variations of the sequence in which thereagents are applied will be obvious to those skilled in the art.

The first technique described above is diagrammatically illustrated inthe accompanying drawing. Referring thereto, protein fiber 1 isimpregnated in step 2 with a solution of the reducing agent. Theresulting treated fiber is then impregnated in step 3 with a solution ofN,N'-methylene bis-acrylamide and the oxidizing agent. There is thusproduced a protein fiber 4 having N,N'- methylene bis-acrylamidepolymerized in situ thereon.

In treating the fiber with the solutions of the N,N'- methylenebis-acrylamide and the redox catalysts, it is preferred that thesolutions contain a wetting agent to enhance the penetration of thereagents into the fiber. One may use for this purpose any of the agentswhich possess surface-active properties and are useful in wetting anddetergent applications. Such agents are exemplified by soap, long chainalkyl sodium sulphates or 'sulphonates, sodium alkyl benzenesulphonates, sodium alkyl phenol sulphonates, sodium di-alkylsulphosuccinates, sulphated or sulphonated esters or amides ofhigh-molecular weight fatty acids, and so forth. There may also be usednon-ionic surfaceactive agents such as for example mannitol laurate andethylene oxide reaction products with fatty acids, fatty alcohols,polyhydric alcohols, or with esters of polyhydric alcohols and highmolecular weight fatty acids.

The time of treatment of the fiber with the amide and the redox catalystsystem may be varied in accordance with the concentration of the amidein the treatment solution, the temperature and the amount ofmodification of the fiber desired. In many cases, a treatment time of 30minutes is adequate to obtain a high degree of shrinkproofing. Thetemperature of the treatment is usually about 40 C. or above. To preventdamage to the wool it is preferred to use a temperature not higher thanabout C. A reaction temperature of about 60 C. is preferred as yieldingrapid polymerization Without damage to the fiber. Such conditions asconcentration of reagents, time and temperature of reaction, etc. arenot critical but may be modified to suit individual circumstanceswithout changing the basic nature of the present invention. In generalthe shrinkproofing efiect will increase with increasing uptake of amidebut not necemarily in linear proportion. As shown in the exampleshereinafter uptakes of the amide on the order of 10% will virtuallyeliminate shrinkage. It is obvious that, depending on the desiredeffect, more or less of the amide may be polymerized on the fiber. Ingeneral uptakes in the range from about 5% to about 15% are preferred.

The process of the present invention is applicable generically toproteinous fibers or their mixtures with other textile fibers whetherthe fibers are in such form or in the form of thread, yarn, knittedgoods, woven goods, and so forth. The invention is particularly adaptedto the treatment of wool but may also be applied to other proteinousfibers such as silk, fur, mohair, other fibers from fleece-bearinganimals, synthetic protein fibers made from zein, peanut protein,casein, keratins, etc.

The invention is further demonstrated by the following example. ExampleI An aqueous solution containing 0.5% hydrazine sulphate and 0.05% ofsodium alkyl (C -C benzene sulphonate was prepared. Swatches of woolencloth were immersed in the solution then centrifuged to remove theexcess liquid. The swatches were then each immersed in an aqueoussolution containing N,N-rnethylene bis-acrylamide (concentrationspecified below), 0.5% hydrogen peroxide, and 0.05% sodium alkyl (C Cbenzene sulphonate. The solutions were maintained at 60 C. and the clothsamples were kept therein for various lengths of time (as specifiedbelow). The samples were then removed from the solution and centrifugedto remove excess liquid then washed thoroughly to remove the unreactedmaterials. The treated samples were subjected to analysis to determinethe uptake by the fibers of the amide. Samples of the treated cloth anda sample of the orginal, untreated cloth were subjected to a standardlaundering technique and the area shrinkage of each sample was thendetermined. The conditions used and the results obtained are tabulatedbelow:

Concentration Uptake of Area of N ,N-meth- Time of N,N-methshrinkageSample ylene bisreaction, ylene bisafter acrylamide in minutesacrylamide, laundering, treating bath, percent percent percent catalystsystem to polymerize the N,N'-methylene bisacrylam-ide in situ on thesaid proteinous textile fibers.

3. A process for shrinkproofing wool fibers comprising treating the woolfibers with N,N'-methylene bisacrylamide in the presence of a redoxcatalyst system to polymerize the said N,N'-methylene bis-acrylamide insitu on the said wool fibers.

4. A process for shrinkproofing wool fibers comprising impregnating thewool fibers with a hydrazine salt and then treating the impregnated woolfiebrs with a solution containing N,N-methylene bis-acrylamide andaperoxygen compound to polymerize the said N,N'- methylenebis-acrylamide in situ on the said wool fibers.

5. A process for shrinkproofing wool fibers comprising impregnating thewool fibers with hydrazine sulfate and then treating the impregnatedwool fibers with a solution containing N,N-methylene bis-acrylamide andhydrogen peroxide to polymerize the said N,N'-rnethylene bisacrylamidein situ on the said wool fibers.

6. A modified proteinous fiber which exhibits reduced shrinkageproperties as compared with the unmodified proteinous fiber comprising aproteinous fiber having N,N-methylene bis-acrylamide polymerized in situthere- 7. A modified proteinous textile fiber which exhibits reducedshrinkage properties as compared with the unmodified proteinous textilefiber comprising a proteinous textile fiber having N,N-methylenebis-acrylamide polymerized in situ thereon.

8. A modified wool fiber comprising a wool fiber having N,N'methylenebis-acrylamide polymerized in situ thereon.

References Cited in the file of this patent UNITED STATES PATENTS StrainSept. 12, Lundberg July 12, Jones May 23, Kropa June 3, Hammer et al.July 7, Melamed Dec. 13,

FOREIGN PATENTS Great Britain Apr. 7, Great Britain Oct. 31,

OTHER REFERENCES Lipson et al.: Formation of Polymers in Textile Fibres,Nature, vol. 157, No. 3992, May 4, 1946, p. 590.

8. A MODIFIED WOOL FIBER COMPRISING A WOOL FIBER HAVING N,N''-METHYLENEBIS-ACRYLAMIDE POLYMERIZED IN SITU THEREON.